Myasthenie.com

Muscle Nerve. 2021 Jun 15. doi: 10.1002/mus.27353. Online ahead of print.

ABSTRACT

INTRODUCTION/AIMS: Videonystagmography (VNG) which directly records eye movements using infrared video goggles with mini-cameras, is used to measure nystagmus. Our aim is to explore whether VNG can be used to detect a decrement in the extraocular muscle (EOM) activity of patients with myasthenia gravis (MG).

METHODS: Thirty-four patients with MG, including 13 with ocular-predominant and 21 with generalized MG and 23 healthy controls participated. Using VNG we recorded the velocity of the eye movements of the patients as they followed a moving target. We then calculated the gain by dividing the eye movement velocity (degrees/second) by the target velocity (degrees/second).

RESULTS: In MG subjects, the mean initial gain (maximum gain) was 1.23±0.31 (range: 0.63-2.15) for the right eye and 1.22±0.37 (range; 0.60-2.28) for the left eye. The mean minimum gain was 0.11±0.12 (0.01-0.58) for the right and 0.14±0.5 (0.02-0.55) for the left. Due to fatigue, the movement gain was reduced by 91.7% in the right eye and 88.2% in the left eye. After reaching minimum velocity, gain remained at a minimum for a mean of 1.08±0.52 (0.3-2.4) seconds for the right and 1.49±0.85 (0.4-3.6) seconds for the left, before the velocity increased again. There was no fatigue-induced decrement in healthy subjects.

DISCUSSION: Our study documents a decrement in EOM activity recorded by VNG in patients with MG which begins to improve within one to two seconds after reaching minimum velocity, analogous to traditional low-frequency repetitive nerve stimulation testing and its U- shaped pattern. Thus, VNG may be a promising diagnostic test for MG.

PMID:34131928 | DOI:10.1002/mus.27353


Source: https://pubmed.ncbi.nlm.nih.gov/3413192 ... 0&v=2.14.4